<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>二级菜单</title>
    <style>
        div{
            margin: auto;
        }
        li{
           list-style: none; 
        }
        .u2{
            display: none;
            position: fixed;
        }

        .u1>li{
            float: left;
            margin-left: 50px;
        }

        .u1>li:hover .u2{
            display: block;
        }

        </style>
</head>
<body>
    
   <ul class="u1">
       <li>奶茶
       <ul class="u2">
           <li>珍珠奶茶</li>
           <li>布丁奶茶</li>
           <li>香草奶茶</li>
       </ul>
    </li>
        <li>果茶
       <ul class="u2">
        <li>珍珠奶茶</li>
        <li>布丁奶茶</li>
        <li>香草奶茶</li>
    </ul>
</li>
    <li>咖啡
    <ul class="u2">
        <li>珍珠奶茶</li>
        <li>布丁奶茶</li>
        <li>香草奶茶</li>
    </ul>
</li>
   </ul>

</body>
</html>